HeyBub wrote:

How about a dive watch? Strap it to something heavy enough to stay
put on the bottom of the pool (a rock, a chunk of brass) and then you
don't need a suction cup.

How about just a plain old waterproof watch?

Also an ordinart $3.50 wall clock from Walmart encased in a clear
plastic bag would work.

But not the kind that need to be plugged into an outlet....